It is difficult to attain a blurring effect (bokeh effect), around which a subject is positively brought into a non-focused state, in a popular digital camera, compared to a general silver salt camera. This is because, since the digital camera has an imaging element smaller in size than the silver salt camera, the blurring amount in a front focus and a rear focus becomes small, even if an equivalent f-value (equivalent focal length) or F-number (NA: Numerical Aperture) is equivalent. In recent years, a digital camera, particularly a digital camera mounted to a cellular phone, has been expected to take a photo with high image quality and high performance quality. Therefore, it has been expected that it can provide a blurring effect, similar to the effect obtained by a large-diameter lens, for example, in which a blurring occurs in the front focus and the rear focus. A technique of applying the blurring effect by a computation process in an image processing circuit has conventionally been proposed.
When a desired blurring effect is performed on an image, a technique of utilizing a function of image filter software on a personal computer (PC) has been known, for example. If the function described above is adapted to an imaging apparatus without performing any changes, a frame memory for storing image data for every frame and a circuit structure that can execute a complicated computation process with high speed are needed. A digital camera, particularly a digital camera mounted to a cellular phone, has strongly been demanded to be downsized, to be power saving, and to have reduced cost. Therefore, in an imaging apparatus having relatively smaller sensor size and a lens having a small diameter, it has been desired to realize a high performance quality due to the application of the blurring effect with a compact, power-saving, and cheap configuration.